♀ Oestrogen
The main female reproductive hormone. It is produced in the ovary. At puberty, eggs begin to mature and one is released about every 28 days.
Hormonal Coordination in Humans » Hormones in Human Reproduction
What you'll learn this session
Study time: 30 minutes
AQA spec: 4.5.3.4
- What reproductive hormones do at puberty
- The main hormones made by the ovary and the testes
- The roles of FSH, LH, oestrogen and progesterone in the menstrual cycle
- Higher tier: how these hormones interact, and how to read hormone graphs
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Unlock This CoursePuberty and the main sex hormones
Hormones control how the human reproductive system develops and works. During puberty, reproductive hormones cause secondary sex characteristics to develop. These are the body changes that mark the move from child to adult.
In girls, these include breast development and wider hips. In boys, they include a deeper voice, facial hair and broader shoulders. Both sexes grow body hair.
♂ Testosterone
The main male reproductive hormone. It is produced by the testes and it stimulates sperm production.
Key terms:
- Puberty: the time when reproductive hormones make the body develop towards adulthood.
- Secondary sex characteristics: body changes at puberty, such as a deeper voice or breast development.
- Oestrogen: the main female reproductive hormone, made in the ovary.
- Testosterone: the main male reproductive hormone, made by the testes.
- Ovulation: the release of a mature egg from the ovary.
Ovulation and the menstrual cycle
From puberty, an egg matures in the ovary and one is released approximately every 28 days. This is called ovulation. The whole sequence of events, repeated about every 28 days, is the menstrual cycle of a woman.
The cycle has two jobs. It matures and releases an egg, and it prepares the lining of the uterus (womb) in case a fertilised egg arrives. If no fertilised egg arrives, the lining breaks down and leaves the body. This is the monthly period.
Several hormones are involved. Each one has its own job:
FSH
Follicle stimulating hormone causes maturation of an egg in the ovary.
LH
Luteinising hormone stimulates the release of the egg.
Oestrogen and progesterone
Both are involved in maintaining the lining of the uterus.
Key terms:
- Menstrual cycle: the monthly cycle of egg maturation, ovulation and changes to the uterus lining.
- FSH (follicle stimulating hormone): causes an egg to mature in the ovary.
- LH (luteinising hormone): stimulates the release of the egg.
- Progesterone: a hormone that helps to maintain the uterus lining.
Quick way to remember
FSH matures the egg. LH lets the egg go. Oestrogen and progesterone look after the lining.
Higher tier only: how the hormones interact
Higher tier only
The hormones do not work alone. Each one affects the others, and this is what controls the cycle. Here is the story in order.
1. The pituitary gland releases FSH. FSH causes an egg to mature in the ovary.
2. The ovary makes oestrogen as the egg matures. Oestrogen helps to rebuild the lining of the uterus.
3. High oestrogen levels stimulate the pituitary gland to release a surge of LH, and they reduce FSH.
4. The surge of LH stimulates ovulation, the release of the egg, around the middle of the cycle.
5. After ovulation, the ovary makes progesterone. Progesterone maintains the lining of the uterus and keeps FSH and LH levels low.
6. If no pregnancy happens, progesterone falls, the lining breaks down and the period begins. The cycle then starts again.
Higher tier only: reading hormone graphs
Higher tier only
Graphs of hormone levels have time (days of the cycle) along the bottom and hormone level up the side. Each hormone has its own line. To read one:
1. Find the line for each hormone from its label or key.
2. Look for the peak of LH. This stimulates ovulation, around the middle of the cycle.
3. Look for which hormone is rising after ovulation. Progesterone rises, so the lining is being maintained.
4. Describe what happens to one hormone while another changes, for example: oestrogen rises, then LH peaks.
Worked example
A graph shows LH rising sharply and peaking in the middle of the cycle. Progesterone stays low until then and then rises. What happens at the LH peak? The LH peak stimulates ovulation, so an egg is released. The rise in progesterone afterwards helps to maintain the uterus lining.
Worked example
A woman's graph shows oestrogen rising steadily for 12 days before LH peaks. Why does LH peak? High oestrogen levels stimulate the pituitary gland to release a surge of LH. The LH then stimulates the release of the egg, which is ovulation.
Common mistakes
Mixing up FSH and LH: FSH matures the egg, LH releases it. Forgetting that progesterone also helps to maintain the lining, not just oestrogen. Writing that ovulation is the period: ovulation is the release of the egg, the period is the lining leaving the body.
Exam-style question
(a) Name the hormone made by the testes that stimulates sperm production. [1 mark]
(b) Describe the roles of FSH and LH in the menstrual cycle. [2 marks]
(c) Higher tier: A graph shows that progesterone levels are high after ovulation. Explain why this is important. [2 marks]
Model answer
(a) Testosterone (1).
(b) FSH causes maturation of an egg in the ovary (1). LH stimulates the release of the egg (1).
(c) Progesterone maintains the lining of the uterus (1) so that a fertilised egg could develop there if pregnancy happens (1).
Exam tip
Learn one job for each hormone in a short phrase: FSH matures the egg, LH releases the egg. Examiners reward the exact verbs.